To install an extension you need to:

1. Place the extracted extension directory into the chroot, such as /opt/firefox/extensions

2. Ensure the extension is correctly named as its install.rdf id

   root@x220:/opt/firefox/extensions# grep 'kiosk@webconverger.com' kiosk\@webconverger.com/install.rdf em:id="kiosk@webconverger.com"

You can verify this manually with something like:

for i in */; do grep -m 1 -H em:id "${i}install.rdf"; done